Steel process flow

Evolution in steel manufacturing process

Earlier long products, structural steels were made from pencil casted ingots, considering quality factors, there was need to design such process, which can produce better quality, then LRF were introduced, to improve quality of steel chemistry VOD/AOD were added to produce good quality steel.Later considering the increased demand of steel in market, increasing infra-structure, it was necessary to make process simple and achieve mass production and fulfill market demand.

Survival period of steel industriesLater number of industries evolved in manufacturing of steel, competition increased in terms of price, it was difficult to bring down consumables cost, hence it became necessary to automize the machines, reduce process, reduce rejections, and do mass production, but even after this it was unable to survive.Then the latest technology HOT-Charging was introduced, in which the steel casted in caster was directly feeded in rolling mills.This new process reduced cost of preheating of billets and metal burning in pre-heating furnace, the cost of billet heating and metal burning accounts more than 50% of steel mfg value in rolling mills, this saving acted as a survival for steel plants, many mini steel plants, which don’t have melting and casting facility have stopped their plants.But even after this success, there is tough competition, hence to reduce cost, rough profiling of steel started itself in casting process. Now a days, Plates, H-Beam, Slab, Round are directly casted in caster, and is rolled further or heat-treated if required to achieve grain structure.

Processing cost of steelThe margin in flat and long product business is very lessScrap value: 25Rs/Kg ( Mild steel)---Yield 95%Melting and casting cost: 7Rs/ KgRolling cost: 2Rs/Kg-------7Rs/KgSale value of TMT: 36Rs/Kg Avg.Sale value of Channels/Plates/Flats: 42Rs/Kg Avg.

Considering the above factors, we can analyze the same condition with seamless pipes, due to increased competition it is becoming difficult for survival of industries, and rejections is accounting a huge cost.Hence it has become necessary to opt for a process which can achieve mass production and gives higher yield, low rework.

Modified process proposalContinuous casting is widely used now a days in manufacturing steel billets, Rounds, slabs. Why cant we utilize this process for manufacturing seamless pipe?? Currently Pipes are manufactured by following processMelting of metal scrap Casting of liquid metal Preheating In furnace Scale removal Rolling Mill Billet heating Piercing Mill Sizing mill Cold processing Surface treatment/Finishing

Shape deformation of pipe from scrap

Scrap

Billet

Round bar

M. Hollow Pipe

Scrap

Round Billet M. Hollow

Pipe

Cast-hollow

Pipe

Continuous casting of steel to form Mother-pipe

Continuous casting of pipes process can be utilized, theoretically there are many positive factors for this technology.Maas production.Low utilization of energy.Low man-work utilization.Higher yield.Lower rejection.Heating of billets at 2 places can be restricted, one before rolling and second before piercing, Hot casted pipe can be directly feeded in sizing mill to reduce thickness, and can be finished in cold rolling mills.

GA for Continuous casting of pipe

Expected Positive results •Using this technology we can manufacture any type of grade, even that grade which is not possible in extrusion/piercing.•In casting process the size will be fixed, as mould and mandrel will have fix size, hence chances of size variation, Eccentricity will be reduced.•Low friction, hence no chances of Lamination, Fracture, or mechanical marks.•Good strength as the flow of material will be in spiral direction, and straight flow in sizing mill, which will form a good strength material.•Higher yield, as the material will have very low scale loss, hence it can be well planned into required length and cut into pieces online.•A great saving to nation and a step toward eco-friendly tech, as it will reduce usage of fuel in preheating furnace.•Requires very less manpower, as this technology is highly automated.•Saving in transportation cost, since all process has to connected in one unit, which will add a major saving.•Good tracking of material, according to orders, as the process will be total online.

Negative factors•The most important factor is quality, because once the heat is casted, it cannot be changed, hence a close monitoring and fast analysis of chemistry is required, to gain the required chemistry, the lab should have all required equipments to analyze Chemistry/Impurities/Ferrite.•Sizing mill is must to reduce the thickness, because in this technology, the thickness of pipe will be above 30mm, which has to be reduced in sizing mill, and finish the surface of pipe, according to standards.•Since the technology is new for seamless pipes, it is quite difficult for promoter to believe in this technology, which can be convinced, by studying and taking suggestions from metallurgists.

Reference documents on Google

www.nrel.gov/docs/fy00osti/26739.pdfhttp://link.springer.com/article/10.3103%2FS0967091212120091#page-1https://www.researchgate.net/publication/257912044_Production_of_hollow_continuous-cast_billet_for_seamless_pipe

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